Merge #7487: Workaround Travis-side CI issues
149641e Travis: Use Blue Box VMs for IPv6 loopback support (Luke Dashjr)
c01f08d Bugfix: depends/Travis: Use --location (follow redirects) and --fail [on HTTP error response] with curl (Luke Dashjr)
5d1148c Travis: Use curl rather than wget for Mac SDK (Luke Dashjr)
1ecbb3b depends: Use curl for fetching on Linux (Luke Dashjr)